This invention relates to a system and method for dewatering or separating particles from a demineralized liquid or colloidal suspension which uses an electrofilter assembly for attracting the particles.
Almost every particle occurring in nature has an inherent electrical charge. This charge can be utilized to achieve a separation as in electrophoresis. Electrophoresis is the movement of charged particles in a conductive liquid or colloidal suspension within an electric field. Charge on the particles may be altered by changing the pH, conductivity, temperature or composition of the solution to be separated. Electroosmosis is the movement of liquid as a function of an applied electric field. The rate of movement of the particles or molecules is generally directly proportional to the amount of applied field (voltage). Another factor which influences rate is the size of the particles or molecules.
When charged particles are placed between the anode and cathode of an electrochemical cell, the particles will tend to migrate towards an electrode as a function of their charge. For example, kaolin clay particles dispersed in water at pH 7 are negatively charged so they migrate towards the anode. Liquid near the particles tend to move towards the cathode. Salts, such as sodium chloride, will be ionized and the ions will move towards the electrode of opposite charge.
Accordingly, the kaolin clay dispersion can be dewatered and demineralized by placing the clay suspension within an electrochemical cell and applying a direct current. The clay particles settle or deposit on the anode surface and on each other, displacing water or liquid molecules to form a more dense, cake layer or slurry with a higher solids content than that of the liquid or aqueous suspension. The anode is removed from the cell and the dense layer of clay particles is recovered by removing the layer from the anode. The water is collected and removed at the cathode.
Variables affecting the performance of an electrochemical cell include the surface area of the electrode, the presence of and nature of the catalyst metal and/or conductive metal of the electrode, contaminants in the reactants and the nature of the reactions taking place in the cell. It is always desirable to not only improve the stability of the electrode and other elements of the electrochemical cells, but to improve the rate of operation and efficiency of the electrochemical cell and the quality of the resulting product.
It is therefore an object of the present invention to provide an electrofiltration system and process which increases the throughput during electrofiltration.
Accordingly, another object of the present invention is to provide an electrofiltration system and process which increases the efficiency and rate of dewatering during electrofiltration.
It is yet another object of the invention to provide an electrofiltration system and process which improves the kaolin clay product during electrofiltration.